Redox flow batteries (hereinafter referred to as “RF batteries”) are batteries that perform charging and discharging using the difference in oxidation-reduction potential between ions contained in a positive electrode electrolyte and ions contained in a negative electrode electrolyte. As illustrated in FIG. 23, an RF battery 1 includes a battery cell 100 that is separated into a positive electrode cell 102 and a negative electrode cell 103 by a membrane 101 that allows hydrogen ions (protons) to permeate. The positive electrode cell 102 contains a positive electrode 104 and is connected via ducts 108 and 110 to a positive electrode electrolyte tank 106 that stores a positive electrode electrolyte. Similarly, the negative electrode cell 103 contains a negative electrode 105 and is connected via ducts 109 and 111 to a negative electrode electrolyte tank 107 that stores a negative electrode electrolyte. The electrolytes stored in the tanks 106 and 107 are circulated within the electrode cells 102 and 103 by pumps 112 and 113, respectively, during charging and discharging.
As illustrated in the lower drawing of FIG. 24, the battery cell 100 is usually formed inside a structure referred to as a cell stack 200. As illustrated in the upper drawing of FIG. 24, the cell stack 200 has a structure in which a cell frame 120 including a bipolar plate 121 integrated into a frame 122 shaped like a picture frame, a positive electrode 104, a membrane 101, and a negative electrode 105 are stacked in that order. In this structure, a battery cell 100 is formed between the bipolar plates 121 of the adjacent cell frames 120.
In the cell stack 200, the flow of the electrolytes through the battery cell 100 is performed by using liquid supply manifolds 123 and 124 and liquid discharge manifolds 125 and 126 which are provided on the frame 122. The positive electrode electrolyte is supplied from the liquid supply manifold 123 through a groove formed on one surface side (front side of the sheet) of the frame 122 to the positive electrode 104 disposed on the one surface side of the bipolar plate 121. The positive electrode electrolyte is discharged through a groove formed on the upper part of the frame 122 to the liquid discharge manifold 125. Similarly, the negative electrode electrolyte is supplied from the liquid supply manifold 124 through a groove formed on the other surface side (back side of the sheet) of the frame 122 to the negative electrode 105 disposed on the other surface side of the bipolar plate 121. The negative electrode electrolyte is discharged through a groove formed on the upper part of the frame 122 to the liquid discharge manifold 126.
Each of the electrodes 104 and 105 that form the battery cell 100 is often formed of a porous conductive material so that a flow of an electrolyte which is a fluid does not block a flow of the electrolyte flowing from the liquid-supply side to the liquid-discharge side. For example, a carbon felt or the like is used (for example, PTL 1).